1. Field of the Invention
The present invention relates to an elastic crawler in a crawler traveling device used on a civil engineering machine, a construction machine, an agricultural machine, and the like.
2. Description of the Related Art
There is known, as a traveling device such as a civil engineering machine, a crawler traveling device traveling by providing a pair of drive sprockets (drive wheels) on respective sides in one of the forward and backward directions, providing a pair of idlers (rolling wheels) on respective sides in the other direction, and causing an endless belt-like elastic crawler wound around a plurality of rollers to circulate circumferentially.
The elastic crawler is composed of: an endless belt-like crawler body made of an elastic material such as rubber; and transversely extensive metal cores partly embedded in the body and circumferentially arranged at uniform intervals. In view of a high tension acting on the elastic crawler in the circumferential direction, a tensile body circumferentially surrounding the ground side of the metal cores is embedded in the elastic crawler.
The tensile body is configured, for example, so that both ends of each of tensile cords such as steel cords are overlapped (lap-jointed) with each other in the crawler body, the tensile cords are wound by one turn in the circumferential direction of the elastic crawler and arranged in the transverse direction of the crawler.
In such a tensile body, the inner-side end of the tensile cord, when traveling on the drive sprockets and the idlers, is less deformable than the other parts of the tensile cord. This causes a greater strain in the elastic body between the inner-side end of the tensile cord and a part of the tensile cord outside the inner-side end. Repeated strain develops fatigue on the strained part of the elastic body to cause damage such as cracking to the strained part, resulting in facilitated removal of the elastic body off the tensile body.
To address this problem, Japanese Unexamined Patent Publication JP-A 2006-315432 discloses a technique to eliminate cracking on the elastic body. Here, a portion of the tensile cord immediately beside the outer-side cord of the overlapping portion where the overlapping portion turns into a single cord is bent inwardly to render the outer-side cord of the overlapping portion an inwardly inclined portion, so that the inner-side end of the tensile cord is in immediate vicinity of the inwardly inclined portion. JP-A 2006-315432 also discloses a technique to improve durability of the elastic crawler by providing bent portions inclined in the same direction on the overlapping portion in the vicinity of both ends of the tensile cord.
The technique of inwardly bending a portion of the tensile cord immediately beside the outer-side cord of the overlapping portion where the overlapping portion turns into a single cord, as disclosed in the JP-A 2006-315432, has the following disadvantage. A great distortion is applied to the elastic body in the vicinity of the bent portions when the ends of the tensile cord travel on the drive sprockets and the idlers of the traveling device, thus failing to provide sufficient prevention of cracks on the elastic body.
The technique of providing the bent portions inclined in the same direction on the overlapping portions in the vicinity of both ends of the tensile cord, as disclosed in the JP-A 2006-315432, has the following disadvantage. Since the inner-side end of the tensile cord overlaps with the outer-side tensile cord in parallel as observed in the conventional art, the strain applied to the elastic body between the inner-side end of the tensile cord and the outer-side tensile cord in the vicinity of the inner-side end cannot be reduced.